[20250210] BOJ / 골드5 / 하노이 탑 / 신동윤

Author: 03do-new30

03do-new30/202502/10 BOJ G5 하노이 탑.md

@@ -0,0 +1,50 @@
+```java
+import java.io.*;
+import java.math.BigInteger;
+import java.util.*;
+
+class Main {
+	
+	private static int N;
+	private static StringBuilder sb;
+	
+	public static void main(String[] args) throws IOException {
+		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
+		BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(System.out));
+		
+		N = Integer.parseInt(br.readLine());
+		sb = new StringBuilder();
+		
+		BigInteger bigTwo = new BigInteger("2");
+		
+		// bw.flush()를 생략하면 틀리는 이유?
+		// N=20일때, 아래 스트링빌더에 쓴 것도 같이출력해줘야 해서 bad -> flush를 해주면 통과하는구나
+		bw.write(bigTwo.pow(N).subtract(BigInteger.ONE) + "\n");
+		bw.flush();
+//		System.out.println(bigTwo.pow(N).subtract(BigInteger.ONE));
+		if (N <= 20) {
+			hanoi(N, 1, 3);
+			bw.write(sb + "");
+		}
+		
+		br.close();
+		bw.flush();
+		bw.close();
+	}
+	
+	private static void hanoi(int disks, int start, int end) {
+		if (disks == 1) {
+			sb.append(start + " " + end + "\n");
+			return;
+		}
+		int via = 6 - start - end; // 경유지
+		hanoi(disks-1, start, via);
+		hanoi(1, start, end);
+		hanoi(disks-1, via, end);
+	}
+}
+
+```
+
+- BigInteger
+- BufferedWriter 사용 시 주의